Process of making carbon dioxide



(No Model.)

s. OAB.OT. PROCESS OF MAKING GARBON DIOXIDE.

415,090- PatentedNov. 12, 1889.

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' UNITED [STATES PATENT OFFICE.

SAMUEL OABOT, OF BOSTON, MASSACHUSETTS.

PROCESS OF MAKING CARBON DIOXIDE.

SPECIFICATION forming part bf Letters Patent No. 415,090,dated Noveinber12,1889. Application filed June '7, 1889. Serial No. 313,495- (Nospecimens.)

To all whom it may concern.-

' zen of the United States, residing at.Boston,

in the county of, Suffolk and State of Massachusetts, have inventedcertain new and usef ul Improvements in the Manufacture of Carbonic-AcidGas, of which the following is a specification.

The object of my invention is the production of pure carbonic'acid gasin large quantities and at moderate'cost.

In a United States patent granted to me on the 29th day of March, 1887,and numbered 359,996, a method is described of treating broken limestonealternately with direct heat and with steam, and collecting or using thecarbon dioxide which is disengaged, while the steam is passing over thehot carbonate before or after the condensation of the wa In said patentthe necessity was stated of alternating continuously the two acts of theprocess cited, so as perpetually to restore the heat which the carbonatelost durin g the passage of the steam by the direct action of firethereon, and then, by means of fresh steam following each heating, toeffect thedecomposition of additional quantities of limestone. I havediscovered, and experience has proved the practicable' nature of thediscovery, that the alternation described is not a necessary conditionof success, that itis not even necessary (though sometimes desirable) tosubject the broken limestone to a preliminary heating by direct fire.

My present invention, in its simplest form, consists, essentially,-intreating broken limestone with strongly superheated steam only. I havefound that steam raised to a temperature somewhat below that of meltingooppersay about 2,000 Fahrenheit-is capable of expelling the carbondioxide from limestone when the latter is enveloped in acontinuously-changing atmosphere of such steam.

In the drawing which forms a part of this specification, thefigurerepresents the apparatus which may be employed to carry out myprocess.

The shaft 10 of the kiln is shown in vertical section. Into this thebroken limestone is charged, the flat cover 12 being removed for thatpurpose. \Vhen this cover is restored to its place and cemented roundabout its edges with fire-clay, and the iron door 14 Be it known that I,SAMUEL CABOT, a citibelow has also been properly screwed 'up againstsuitable packing, the superheated steam is admitted through the channel16 from the superheater 18 to the lower part of the kiln.

The best form of superheater need'not be here discussed, as the subjectis well understood, and any efficient construction may be employed. Ishow this necessary part of my apparatus therefore only in elevation,and indicate with dotted lines the iron and fireclay tubes which may beemployed, as also the position of the boiler in. which the requisitesteam is generated, the waste heat from the furnace below being used forthat purpose. I Y

W hen the steam from the superheater 18 enters the closed kiln throughthe channel 16, its heat will first be expended solely in rais ing thetemperature of the mass of cold limestone in the shaft 10. Pending thisheating the valve at 22 is open, so that the cooled steam in the kiln ispermitted to discharge and to give place for a continuous stream ofexceedingly hot steam through the channel 16. stances the temperature atwhich decomposition of the calciumcarbonate begins is remarkably low;but that as the temperature of the stone is raised above that therapidity with which carbon? dioxide is evolved is greatly increased, sothat it may be said generally that the more efficient the superheaterthe better and more economical will be the result. When once thedecomposition has been started in a kiln of this sort, it can bemaintained indefinitely. This is done by feeding at intervals small'quantities of broken limestone above and raking away equivalentquantities of burnt lime from the discharge-openin g below, which isthen to be quickly and tightly closed by the door 14, the interruptionto the continuous evolution of gas being made as short as possible. Thequantity of quicklime produced during each interval will extend a shortway up the shaft of the kiln close above the channel 16. The gas andsteam as they escap through the valve 22 may be cooled by suitablemethods, so as to precipitate the latteras water, in which case a verypure carbonic acid will be I have found that under these circumby directheat, not only because the way hereinbefore set forth is slow andcostly, but also for the more vital reason that the large condensationof Water which takes place upon the cold stone and fire-brick is liableto inj me the kiln very seriously. I therefore prefer to avail myself ofdirect heat for this first heating, and I accomplish the same by forcingin under suitable pressure an inflammable gas, which may be supplied bythe tubes 24 and 26, and atmospheric air to support combustion throughindependent tubes or through indraft-openings, as indicated by thearrows at 28, all leading to the combustionchamber 30, located near thelower part of the shaft.

valve 36 and the annular opening at 28 is raising the temperature of thekiln and its contents, the cover 12 is 01f the top, so that the productsof the combustion may escape, especially the large volume of nitrogen,which dilutes whatever carbonic acid may be formed under suchcircumstances; but as soon as ever the necessary heat has been reachedboth the inflammable gas or vapor and the air which enabled it to burnare cut ofi, the cover 12 closed, and the subsequent running of the kilncarried on with superheated steam alone.

In the figure the design of the kiln therein shown in section is welladapted for the ends in view; but it is obvious that it might be variedinfinitely in form and plan and still be as suitable for theconsummation of the process I have invented. Such modifications inconstruction will be desirable, for instance,when the completedecomposition of one large charge of calcium carbonate is accomplishedand all the caustic lime removed before the next lot is introduced. Sucha procedure is often very convenient, especially when suitpoint by theaid of super- 3 \Vhile the flame so distributed and 1 controlled as toquantity and quality by the able fuel is to be had to heat withoutdifficulty the large mass in the first instance. My process will then befound especially favor able, as there is little or no danger ofoverheating the burnt lime, the value of which byproduct isconsiderable.

In this specification the special devices by means of which my processis worked are not claimed, as it is intended that they should form thesubject-matter of a future application for patent.

What I claim is- 1. The improvement in the manufacture of carbondioxideavhich consists in first raising the temperature of calciumcarbonate to the degree requisite for its decomposition in an atmosphereof water vapor by the action of superheated steam thereon, and thenmaintaining such temperature and decomposition by continuing the flow ofsuperheated steam over said carbonate until the disengagement of itscarbon dioxide is accomplished, substantially as described.

2. The improvement in the manufacture of carbon dioxide, which consistsin first raising the temperature of calcium carbonate to the degreerequisite for its decomposition in an atmosphere of water-vapor bydirecth eat from any suitable source, then cutting off and removing thesame, and then maintaining such temperature by a continued flow ofsuperheated steam over said carbonate until the disengagement of itscarbon dioxide is accomplished, substantially as described.

8. In the manipulation of calcium carbonate for the production of carbondioxide and quicklime, the preliminary heating of said carbonate by thedirect application of burning gases, then cutting off the gaseous fueland admitting a current of superheated steam, whereby the necessarytemperature is maintained and the desired decomposition effected,substantially as described.

4. In the decomposition of calcium carbonate for the production of amixture of pure carbon dioxide and water-vapor, the treating of saidcarbonate with a current of superheated steam at or near the temperatureof melting copper, substantially as described.

SAM. CABOT.

Witnesses:

CHAS. P. NICHOLS, T. F. ROBINSON.

